Sealing unit for a fuel pressure sensor

ABSTRACT

The invention relates to a sealing unit for a fuel pressure sensor for sealing an at least virtually flat sealing joint between the sensor and a component that carries it via a screw connection, wherein a round sealing washer with a central bore is disposed between the threaded bolt-shaped end of the sensor housing with its central sensor bore and the bottom of the threaded bore of the component with its central pressure fluid opening. A pin is formed onto the threaded bolt-shaped end of the sensor housing, which pin centers the sealing washer, fixing it in a positive and/or frictional, non-positive manner, and rises above an end face that serves as a bearing surface for the sealing washer. The pin ends in an end face and has a length that is shorter than the thickness of the sealing washer. A sealing unit is produced that assures a reliable sealing function and permits a simple installation and disassembly of the sealing washer while reclaiming the sealing washer in a sealing position.

PRIOR ART

The invention is based on a sealing unit for a fuel pressure sensor.

As a rule, sealing units of this kind constitute a fuel pressure sensorin combination with a sealing washer. Both parts are separate from eachother. When the fuel pressure sensor is installed in a correspondingthreaded bore of a fuel carrying component, the sealing washer is firstinserted into the bore. A number of difficulties arise in connectionwith this. The threaded bores are often let into the fuel carryingcomponent from the side or even from underneath so that the insertion ofthe sealing washer is difficult simply because of gravity. Also,sometimes the threaded bores are partially or completely impossible tosee into because they are blocked from view by components disposed infront of them, so that the position of the sealing washer before theinsertion of the fuel pressure sensor cannot be optically controlledwithout some means of assistance. Therefore an off-center or tiltedseating of the sealing washer cannot be detected. Consequently, leaks ordamage to the threaded bore or the fuel pressure sensor, which arisewhen the fuel pressure sensor is tightened, are not detected.

Also, in the case of a proper installation, problems can arise at leastduring disassembly of the fuel pressure sensor. The sealing washer isusually still seated at the bottom of the threaded bore after the fuelpressure sensor has been unscrewed. The washer sticks there, among otherthings, by means of adhesion with fuel residues or by means of beingjammed in the thread runout. The subsequent removal is only possiblethrough the expenditure of a considerable amount of time. At the sametime, it includes the danger of mechanically damaging the bottom of thethreaded bore, which serves as the sealing face, which can lead to leakswhen the fuel carrying component is reused.

Furthermore, there is the possibility that the insertion of the sealingwasher will be forgotten.

In order to avoid the disadvantages associated with the prior artdescribed, a sealing unit must be produced, which assures a reliablesealing function and a simple installation and disassembly of thesealing washer.

ADVANTAGES OF THE INVENTION

With the sealing unit according to the invention, a pin is formed ontothe threaded bolt-shaped end of the sensor housing, which pin centersthe sealing washer, fixing it in a positive and/or frictional,non-positive manner, and rises above an end face that serves as abearing surface for the sealing washer. The pin, which ends in an endface, has a length that is shorter than the thickness of the sealingwasher.

Before the fuel pressure sensor is screwed into the fuel carryingcomponent, the sealing washer is placed on the pin. When the pin has acylindrical outer contour, the sealing washer is held on the pin, forexample with the aid of a lateral press fit. The sealing washer can alsobe glued in the region of the pin. The sealing washer is axiallycompressed by means of the tightening of the fuel pressure sensor, bymeans of which a frictional, non-positive connection between the pin andthe bore of the sealing washer is produced or at least reinforced.

Independent of the fixing method, the sealing washer is attached to thefuel pressure sensor so that during storage, transport, installation,and disassembly of the fuel pressure sensor, the sealing washer remainsfixed to the fuel pressure sensor in captive fashion. Consequently, thesealing washer cannot be forgotten during installation, nor can it beinserted into the threaded bore of the component in an off-centermanner. As a result, most of the causes for a leak in the sealing jointbetween the bottom of the threaded bore and the sealing washer areeliminated. Likewise, the fixing of the sealing washer on the pinvirtually rules out the possibly of a leak in the sealing joint betweenthe sealing washer and the pin or the flat bearing surface on thethreaded bolt end. Furthermore, the flat bearing surface is covered andconsequently protected by the sealing washer during storage, transport,and installation.

The pin can alternatively also be embodied in the form of a truncatedcone. In this instance, the cone diameter in the region of the sensorend sealing face is smaller than at the free end of the pin. The sealingwasher is seated on a pin of this kind, for example via a snug fit or aglued connection. The sealing washer can also be fixed by means ofpartial deformations in the region of the pin edge. The deformation ofthe sealing washer is produced at one or more points in the region ofthe pin edge, for example with the aid of tools similar to centerpunches or drift punches. At these points, the material of the sealingwasher is compressed and displaced in sections so that in theselocations, it touches or engages behind the truncated cone-shaped outercontour of the pin.

The complete rear engagement with which the sealing washer material atleast encompasses the outer contour in a virtual ring, is produced whenthe fuel pressure sensor is tightened in the threaded bore. The sealingmaterial is plastically deformed and rests against the outer contour ofthe pin in a sealing, positive, and frictional, non-positive manner.

When the fuel pressure sensor is disassembled, the sealing washer isseparated from the fuel carrying component while being unscrewed,because of the tensile and shear motion in the sealing joint between thesealing washer and the bottom of the threaded bore, and the sealingwasher is removed from the threaded bore along with the fuel pressuresensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention ensue from the following description oftwo schematically represented embodiments.

FIG. 1 shows a screwable end of the fuel pressure sensor with a sealingwasher and an opposing piece;

FIG. 2 shows the screw installed fuel pressure sensor with a truncatedcone-shaped pin and a deformed sealing washer.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows the threaded bolt-shaped end (21) of a fuel pressure sensor(20), a sealing washer (10) and a threaded bore (2) for receiving thefuel pressure sensor (20) in a pressure fluid carrying component (1).The components here are represented in a disassembled state.

The outer contour of the threaded bolt-shaped end (21) includes athreaded section (22), a bearing section (23) adjoining this, and acentering pin (26) formed onto this bearing section. The bearing section(23) has a cylindrical outer contour whose diameter is smaller than thecore diameter of the thread (22). The cylindrical outer contourtransitions into an annular end face (24) via a chamfer. This end face(24) is used as the sensor end sealing face. In FIG. 1, the centeringpin (26) likewise has a cylindrical outer contour, whose diameter isslightly larger than the inner diameter of the sealing washer (10). Thecentering pin (26) ends in an end face (28). The length of the centeringpin (26) is shorter than the thickness of the sealing washer (10).

The threaded bolt-shaped end (21) of the fuel pressure sensor (20) has acentral bore (29), which feeds into the end face (28). The transitionregion is chamfered.

A threaded bore (2) is disposed in the component (1) that carries thefuel pressure sensor (20) and the sensor is seated in this bore wheninstalled. The bottom of the threaded bore (2) is a smooth face thatfunctions as a component end sealing face. The diameter there is matchedin proportion to the outer diameter of the sealing washer (10) so thatthe outer diameter of the sealing washer (10), which increases as aresult of assembly, is reliably smaller than the inner diameter of thethreaded bore (2) or the bottom of the threaded bore.

A pressure fluid opening (3) is disposed centrally in the bottom of thethreaded bore (2).

FIG. 2 shows a fuel pressure sensor (20') in the installed state. Inthis instance, the centering pin (26') of the fuel pressure sensor (20')has an outer contour in the shape of a truncated cone whose diameterdecreases from the free end or from the end face (28) toward thethreaded section (21). When the fuel pressure sensor (20') is tightened,this contour permits a positive connection between the fuel pressuresensor (20') and the sealing washer (10) because of the deformation orthe flattening and mushrooming over of the sealing washer (10).

To this end, before the fuel pressure sensor (20') is screwed in, thesealing washer (10) is attached to the centering pin (26') in captivefashion with the aid of a close, snug fit. In lieu of the snug fitconnection, the un-deformed sealing washer (10) can also be glued to theannular end face (24).

When the fuel pressure sensor (20') is installed, it is inserted intothe threaded bore together with the sealing washer (10) attached to itand is screwed in. After the sealing washer (10) comes into contact withthe component end sealing face, the sealing washer (10) is deformed bybeing pressed flat when the screw connection is tightened as provided.By means of the material displacement among other things, the innerdiameter of the sealing washer (10) is reduced and the outer diameter isenlarged. By means of the deformation of the inner diameter, the sealingwasher (10) engages behind the centering pin (26'), see FIG. 2. Theheight of the sealing washer (10) after the deformation is still greaterthan the height of the centering pin (26').

In a subsequent disassembly, the used, deformed sealing washer (10)adheres to the threaded bolt-shaped end (21) of the fuel pressure sensor(20'). The sealing washer (10) can be separated from the fuel pressuresensor (20') with the aid of cutting pliers, without the danger ofdamaging the sensor in order, if need be, to outfit the fuel pressuresensor (20') for reuse with a new sealing washer (10). This is also truefor the fuel pressure sensor (20) that has a cylindrical centering pin(26). In that instance, the sealing washer (10) can be removed with lessof an expenditure of force since it does not adhere positively to thecentering pin (26).

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A sealing unit in combination with an end of afuel pressure sensor housing, said fuel pressure sensor housing beingsecured to a fluid pressure carrying component which includes a centralpressure fluid opening, said sensor housing includes a centralunobstructed sensor bore (29) through which fuel flows, screw threads(22) along a bolt threaded end (21), a bearing end section (23)adjoining integral with said bolt threaded end and a centering pin (26)extends from said bearing end section, said bearing end section (23)including an end sealing face (24), said component includes a threadedbore (2) to which the sensor housing is secured via said threaded end(21), said sealing unit comprises a disk-type sealing washer (10) with acontrol bore, said sealing washer is permanently deformed and disposedon said centering pin between said sealing face (24) of the bearing endsection (23) of said sensor housing in engagement with said end sealingface (24) and a bottom of the threaded bore of said component, saidcentering pin (26, 26') centers the sealing washer (10) fixing thesealing washer in a positive and frictional manner on said pin, whereinthe pin (26, 26') has an axial length that is shorter than a thicknessof the sealing washer (10).
 2. The sealing unit according to claim 1, inwhich an outer contour of the pin (26) is cylindrical.
 3. The sealingunit according to claim 1, in which the sealing washer (10) is fixed onthe pin (26) by means of a lateral press fit.
 4. The sealing unitaccording to claim 1, in which the pin (26') is embodied in the shape ofa truncated cone, wherein the cone diameter in a region of the sensorend sealing face is smaller than at a free end of the pin (26').